In continuous ink jet printing, electrically conductive ink is supplied under pressure to a manifold region that distributes the ink to a plurality of orifices, typically arranged in a linear array(s). The ink discharges from the orifices in filaments which break into droplet streams. Individual droplets in the streams are selectively charged in the region of the break-off from the filaments, and charged drops are deflected by electrostatic forces from their original trajectories. The deflected drops may be caught and recirculated and the undeflected drops allow to proceed to a print receiving medium.
When the ink jet printhead is not in operation, means must be provided to seal the printhead so that ink doesn't dry in the catcher face area, or weep from the jets and soil the apparatus or adjacent work surfaces. One approach to providing a seal is taught in U.S. Pat. No. 4,928,115 issued May 22, 1990 to Fagerquist, et al which discloses a seal over the printhead when the printhead is not in operation. The seal described in the '115 patent is a sealing wall that slides in a slot between a position where the ink jet charging and deflecting area is open and a position where the charging and deflection area is covered by the sealing wall. The mechanism for moving the sealing wall is located in front of the ink jet printhead and includes a bale arm that controls cams that move the sealing wall.
This prior art arrangement suffers from a number of shortcomings. First, ink may enter the area between the sealing wall and the slot it slides in and when dry, effectively cement the sealing wall into the slot against proper movement. Furthermore, the mechanism for moving the sealing wall occupies a substantial amount of space in front of the printhead, thereby undesirably increasing the footprint of the printhead. Since such printheads are employed in bindery lines where it is desirable to place the printhead as near to the seam of a signature as possible, a minimum sized footprint is desirable.